Transporting Residue of Vehicle Position Data Via Wireless Network

ABSTRACT

The invention relates to compressed data transmission in wireless data communication. Disclosed are methods and apparatuses for transporting residue of vehicle position data via a wireless network. A disclosed method for transporting residue of vehicle position data via a wireless network, includes the steps of: receiving data for updating residue encoding schema from a monitoring server; constructing a residue encoding schema based on the data, thereby producing a constructed residue encoding schema; and storing the constructed residue encoding schema such that the constructed residue encoding schema will become the current residue encoding schema; where: the constructed residue encoding schema is constructed such that each residue of the constructed residue encoding schema corresponds to a code; and the constructed residue encoding schema is constructed such that a residue having a relatively high probability of occurrence corresponds to a code of relatively short length.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from China PatentApplication No. 201210091267.7 filed Mar. 30, 2012 the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to wireless data communication and, in particular,to a method and apparatus for transporting vehicle position data via thewireless communication network system.

2. Description of Related Art

With the development of wireless networks and the popularity of theGlobal Positioning System (GPS), a growing number of transportationcompanies and traffic management departments use wireless networks andthe GPS system to determine the real-time location of a moving vehicle.

In such applications, the GPS device equipped on a vehicle can receivesatellite signals and can determine the position data representing theposition of the vehicle based on the signals. A backend server in chargeof determining the position of the vehicle exchanges information withthe vehicle through a wireless network. The vehicle needs tocontinuously transport the position data determined by the GPS device,consuming a large amount of bandwidth of the wireless network.

U.S. patent application US2006/0244587A1 discloses a method andapparatus of transportation of compressed measurement data in order toreduce the amount of measurement data, such as position data, needing tobe transported via wireless networks. The means of the method forcompressing measurement data is to transport the difference (also knownas “residue”) between the current measurement data and the referencedata, and convert the difference into a variable-length code using aparticular encoding schema, for example, converting an integer “24” asthe difference into a binary “1011 0000”. Since what is actuallytransported is the variable-length code for the difference, the amountof the measurement data needing to be transported is compressed.

SUMMARY OF THE INVENTION

The present invention provides a method for transporting residue ofvehicle position data via a wireless network, includes the steps of:receiving code from a vehicle-mounted terminal; deriving position dataof a vehicle from the code according to a current residue encodingschema; determining whether updating the current residue encoding schemais needed according to context information of the vehicle; generatingdata for updating the current residue encoding schema, if updating thecurrent residue encoding schema is needed; transporting the data forupdating the residue encoding schema to the vehicle, if updating thecurrent residue encoding schema is needed; constructing a residueencoding schema based on the data for updating the current residueencoding schema, thereby producing a constructed residue encodingschema, if updating the current residue encoding schema is needed; andupdating the current residue encoding schema with the constructedresidue encoding schema, if updating the current residue encoding schemais needed; where: the code is code for residue of position data of thevehicle; the vehicle-mounted terminal is located in the vehicle; thecurrent residue encoding schema corresponds to the vehicle; theconstructed residue encoding schema is constructed such that eachresidue of the constructed residue encoding schema corresponds to onecode; and the constructed residue encoding schema is constructed suchthat a residue having a relatively high probability of occurrencecorresponds to a code of relatively short length.

The present invention also provides a method for transporting residue ofvehicle position data via a wireless network, including the steps of:receiving data for updating residue encoding schema from a monitoringserver; constructing a residue encoding schema based on the data,thereby producing a constructed residue encoding schema; and storing theconstructed residue encoding schema such that the constructed residueencoding schema will become the current residue encoding schema; where:the constructed residue encoding schema is constructed such that eachresidue of the constructed residue encoding schema corresponds to acode; and the constructed residue encoding schema is constructed suchthat a residue having a relatively high probability of occurrencecorresponds to a code of relatively short length.

The present invention further provides a monitoring server fortransporting residue of vehicle position data via a wireless network,including: a storage device configured for storing historical data; adata analysis device, configured to generate a normalized residuedistribution of position data of all vehicles that comply with aconstraint condition; an encoding schema updating device, configured tocalculate a probability of occurrence of a residue corresponding to aspecific vehicle according to the normalized residue distribution; andconstruct a residue encoding schema, thereby producing a constructedresidue encoding schema; and, a decoding device configured to derive aresidue, which corresponds to a code, according to a residue encodingschema; where: the historical data includes real-time vehicle positiondata and associated context information; the constructed residueencoding schema is constructed such that each residue of the constructedresidue encoding schema corresponds to one code; and, the constructedresidue encoding schema is constructed such that a residue with arelatively high probability of occurrence corresponds to a code ofrelatively short length.

The present invention additionally provides a vehicle-mounted terminalfor transporting residue of vehicle position data via a wirelessnetwork, including: a data acquisition device, configured to obtainposition data of a vehicle; an encoding schema updating device,configured to calculate a probability of occurrence of a residuecorresponding to the vehicle according to a normalized residuedistribution, and construct a residue encoding schema according to theprobability of occurrence, thereby producing a constructed residueencoding schema; a storage device, configured to store the constructedresidue encoding schema; and an encoder, configured to generate acorresponding code of a residue according to the constructed residueencoding schema; wherein: the vehicle-mounted terminal is located in thevehicle; the constructed residue encoding schema is constructed suchthat each residue of the constructed residue encoding schema correspondsto one code; and the constructed residue encoding schema is constructedsuch that a residue with a relatively high probability of occurrencecorresponds to a code of relatively short length.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an exemplary computing system 100 thatis adapted to be used for implementing embodiments of the invention.

FIG. 2 illustrates a schematic diagram of a prior art system used totrack the position of the vehicle.

FIG. 3 illustrates a block diagram of the system and apparatus fortransporting residue of the position data of the vehicle via a wirelessnetwork according to an embodiment of the invention.

FIG. 4 illustrates a flowchart of the method for transporting residue ofthe position data of the vehicle via a wireless network according to anembodiment of the invention.

FIG. 5 illustrates a flowchart of the method for transporting residue ofthe position data of the vehicle via a wireless network according toanother embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In view of the prior art, the inventors found that, under the samecondition, the amount of variations or residue of the position data ofthe vehicle in moving generally complies with a certain law ofdistribution. The distribution law can reflect the probability ofoccurrence of residue for individual vehicles. Based on that, thecompression encoding schema of the prior art may be improved.

Preferred embodiments of the present disclosure will be described ingreater detail below with reference to the accompanying drawings. Theaccompanying drawings have shown those preferred embodiments of thepresent disclosure, however, it should be understood that, the presentdisclosure can be implemented in various forms, but are not limited tothese embodiments illustrated herein. On the contrary, these embodimentsare provided for making the present disclosure more thorough andcomplete, such that the scope of the present disclosure can becompletely delivered to one of ordinary skill in the art.

Referring to FIG. 1, a block diagram of an exemplary computing system100 which is applicable to implement the embodiments of the presentinvention is shown. In FIG. 1, the computing system 100 may include: CPU(Central Processing Unit) 101, RAM (Random Access Memory) 102, ROM (ReadOnly Memory) 103, System Bus 104, Hard Drive Controller 105, KeyboardController 106, Serial Interface Controller 107, Parallel InterfaceController 108, Display Controller 109, Hard Drive 110, Keyboard 111,Serial Peripheral Equipment 112, Parallel Peripheral Equipment 113 andDisplay 114. Among above devices, CPU 101, RAM 102, ROM 103, Hard DriveController 105, Keyboard Controller 106, Serial Interface Controller107, Parallel Interface Controller 108 and Display Controller 109 arecoupled to the System Bus 104. Hard Drive 110 is coupled to Hard DriveController 105. Keyboard 111 is coupled to Keyboard Controller 106.Serial Peripheral Equipment 112 is coupled to Serial InterfaceController 107. Parallel Peripheral Equipment 113 is coupled to ParallelInterface Controller 108. And, Display 114 is coupled to DisplayController 109. It should be understood that the structure as shown inFIG. 1 is only for the exemplary purpose rather than any limitation tothe present invention. In some cases, some devices may be added to orremoved from the computer system 100 based on specific situations.

As will be appreciated by one of ordinary skill in the art, aspects ofthe present invention may be embodied as a system, method or computerprogram product. Accordingly, aspects of the present invention may takethe form of an entirely hardware embodiment, an entirely softwareembodiment (including firmware, resident software, micro-code, etc.) oran embodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing.

More specific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wire, optical fiber cable, RF, etc., or any suitable combination of theforegoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowcharts and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

To facilitate the understanding of the invention, reference is firstmade to FIG. 2 to describe the prior art techniques for tracking thevehicle position. FIG. 2 shows a prior art system 200 for tracking thevehicle position. The system 200 comprises a backend server 201, awireless network 202 and a vehicle 203. Bidirectional communications maybe performed to exchange information between the backend server 201 andthe vehicle 203 through a wireless network 202.

In order to track the position of the vehicle 203, the backend server201 needs the real-time position data (x, y, t) of the vehicle 203. Thetriplet represents the position coordinates or position data (x,y) at atime t, wherein x represents longitude and y represents latitude. Thevehicle 203 may send its position data to the backend server 201 throughthe wireless network 202. To this end, the vehicle 203 may include adata acquisition device 233. The data acquisition device may acquire thereal-time position data from, for example, a GPS device (not shown)equipped on the vehicle 203. The real-time position data acquired may bestored in a storage device 231. The data acquisition device may obtainthe position data (x0, y0) of time t0 before time t1 from the storagedevice.

The difference or amount of variation between the position data (x1,y1)of the vehicle 203 at the current time t1 and the position data (x0, y0)at an earlier time t0 is referred to as “residue” and denoted asΔx=x1−x0 and Δy=y1−y0 or simply as (Δx, Δy). The vehicle 203 may sendthe residue (Δx, Δy) to the backend server 201. Based on the positiondata (x0, y0) at t0 and the residue (x1−x0, y1 −y0) stored in a storagedevice 211, the backend server 201 may calculate the position data (x1,y1) at time t1 and store it in the storage device. Sending the residueinstead of the position data themselves may reduce the amount of datafor transmission.

Further, the vehicle 203 is equipped with an encoder 232 for encodingthe residue (x1−x0, y1 −y0). The encoder 232 uses an encoding schema toencode a decimal residue value into a binary coding, for example, thedecimal residue of “24” is encoded into the binary “10110000”. Thevehicle 203 may transport the residue coding to the backend server 201.Compared to sending the residue itself, sending the residue coding mayreduce the amount of data for transmission. Accordingly, the backendserver 201 is configured with a decoder 212, which decodes the residuecoding in accordance with the same encoding schema as used by theencoder 233 to obtain the residue (Δx, Δy).

To facilitate narration, in the following description, the term“position data” refers to the position coordinates of the vehicle and isrepresented with such symbols as “x”, “y” or “(x, y)”, or any symbolderived from them. The term “residue” refers to the difference betweentwo position data of adjacent sampling time points is represented withsuch symbols as “Δx”, “Δy” , “(Δx, Δy)” and the like.

The basic idea of the present invention is to analyze the distributionof the residues of the position data of the vehicle at different roadsections according to historical data of moving vehicles. Based on thedistribution of the residues, the probability of occurrence ofrespective residues of the position data of individual vehicles may bederived. The residues are encoded according to the probability of theiroccurrence and a relatively short code is used to represent a residuewith relatively high occurrence probability, resulting in the overallreduction in the data amount of the code to be transported.

Hereinafter, various embodiments of the present invention will bedescribed with reference to the drawings. Refer now to FIG. 3, whichillustrates a schematic diagram of the system according to an embodimentof the invention. The system 300 as shown is comprised of a monitoringserver 301, a wireless network 302 and a vehicle-mounted terminal 303.The monitoring server 301 and the vehicle-mounted terminal 303 mayconduct bidirectional communication via the wireless network 302 toexchange information with each other.

The vehicle-mounted terminal 303 is a computing device deployed in thevehicle, which may be embodied with the computer system 100 shown inFIG. 1. The vehicle-mounted terminal 303 comprises a storage device 331,an encoder 332 and a data acquisition device 333. Their functions arerespectively similar to the storage device 231, the encoder 232 and thedata acquisition device 233 shown in FIG. 2. In addition, thevehicle-mounted terminal 303 also comprises an encoding schema updatingdevice 334.

The monitoring server 301 shown in FIG. 3 may also be embodied with thecomputer system 100 shown in FIG. 1. The monitoring server 301 comprisesa storage device 311 and a decoder 312, their functions are respectivelysimilar to the storage device 211 and decoder 212 shown in FIG. 2. Inaddition, the monitoring server 301 also comprises a data analysisdevice 313, and an encoding schema updating device 314. Components ofthe monitoring server 301 are described in the following.

In the storage device 311 there is stored historical data, whichincludes real-time vehicle position data (x, y, t) and the associatedcontext information. The historical data may be stored in easilysearchable databases. The real-time position data may be the positiondata (x, y) at time t, received from the vehicle-mounted terminal 303.It may also be derived from the residue (Δx, Δy) received from thevehicle-mounted terminal 303, as discussed above with reference to FIG.2.

The context information includes, for example:

The type of vehicle, such as car, truck, bus, etc. The type of anyparticular vehicle in which the vehicle-amounted terminal 303 is locatedmay be recorded when the vehicle-amounted terminal 303 is registeredwith the server 301 for service.

Road section, i.e. a section of road in the road network correspondingto the position data (x, y). The mapping relationship between theposition data (x, y) with the road section may be obtained by using thegeographical information systems (GIS) known in the prior art.

Other context information may also include the weather conditioncorresponding to the time in the real-time position data (x, y, t), forexample, “rainy”, “misty”, etc.

In the database there may be stored the context information inassociation with the real-time vehicle position data (x1, y1, t1), asshown in the following table:

Vehicle -ID Type Road Section Position Time . . . V1 Truck R1 (x1, y1)t1 . . . . . . . . . . . . . . . . . . . . .

The first row of the table contains data names “Vehicle-ID”, “Type”,“Road Section”, “Position” and “Time”. In practical applications, theremay be more such data names. Each of the rows below the first rowrepresents a data value. For example, the data value of the second linedenotes that the vehicle “V1” is of the type “Truck”. At time t1, itsposition is (x1, y1), the corresponding road section being “R1”.

In accordance with an embodiment of the invention, the data analysisdevice 313 may be configured to generate the normalized residuedistribution of the position data of all vehicles complying with certainconstraint condition according to historical data. The historical datamay be obtained from the database stored in the storage device 311.

The constraint condition may be set to be either exactly the same as ormatching the condition of the vehicles being tracked. For example,taking the specific time frame “9:00-9:30”, the specific road section“R1” and the specific vehicle type “truck” as the constraint condition,the calculation of the normalized residue distribution of the positiondata of all vehicles may be divided into the following three steps.

Step 1: A set of real-time position data for all trucks running on theroad section R1 in 9:00-9:30, S, is obtained from the historical data.Each item in the set S may be represented with “(vehicle _ID, x, y, t)”.

Step 2:. The normalized residue of the position data for each of thevehicles in the set S is obtained. The normalized residue of theposition data for a vehicle may be obtained in the following manner.First, the residues of all position data of the vehicle are calculated.In general, if the real-time position data sampled at two adjacent timepoints for a vehicle V1 is P0 =(x0, y0, t0) and P1 =(x1, y1, t1), thenthe corresponding residue is: Δx =x1−x0; Δy =y1−y0. Then, the residue isnormalized with the time interval Δt =t1−t0 to obtain the normalizedresidue: Δx′=Δx/Δt; Δy′=Δy/Δt. For example, the real-time position dataobtained at two adjacent sampling instants with interval of 10 secondsis: P1=(120.67022, 31.26685, 10:01:03); P2=(120.67015, 31.26676,10:01:13). Then the corresponding residue is:Δx=120.67015-120.67022=−0.00007; Δy=31.26676-31.26685 =-0.00009. Theresidue Δx=−0.00007 and Δy=−0.00009 is normalized with Δt=10 seconds toobtain the normalized residue as the following: Δx′=Δx/Δt=Δx/10=−7*10⁻⁶;Δy′=Δy/Δt=Δy/10=−9*10⁻⁶. The above process may be performed for allresidues of one vehicle to obtain all normalized residues of thevehicle. The above process for all vehicles in the set S may beperformed to obtain normalized residues of the position data for allvehicles in the set S.

Step 3: The distribution of all the normalized residues of the positiondata is obtained according to the normalized residues of the positiondata of all vehicles in the set S of all vehicles normalized residue.The distribution complies or approximately complies with the normaldistribution N(μ, σ) and reflects the frequency distribution of allnormalized residues, wherein, μ represents the mean value of the normaldistribution and a represents the standard deviation. For example, thenormalized residues of the position data of the vehicle under certainconstraint condition (9:00-9:30, section R1, truck) comply with thenormal distribution with the mean value μ of 0.0001 and the standarddeviation σ of 0.00002, denoted as N (0.0001, 0.00002). The abovenormalized residue distribution may be stored. For example, thenormalized residue distribution N (0.0001, 0.00002) may be stored inHashmap according to the following mapping relationship: (R1, {9:00-9:30truck})→N (0.0001, 0.00002) . . . mapping (1). A plurality of suchnormalized residue distributions may be calculated in advance and thenstored. For example, another mapping relationship is: (R2, {9:00-9:30truck})→N (0.0001, 0.00003) mapping (2). Wherein “R2” represents a roadsection different from the road section “R1”, and the mapping (2)denotes that, under the constraint condition of {9:00-9:30, road sectionR2, truck}, the normalized residues of the position data of the vehiclecomply with the normal distribution N (0.0001, 0.00003), wherein themean value μ is 0.0001, and the standard deviation σ is 0.00003.

In the above example it is illustrated that the data analysis device 313may generate the normalized residue distribution of the position data ofall vehicles that comply with certain constraint condition based on thehistorical data in the database. The constraint condition may be onethat matches, or is equivalent to, the condition of the vehicle of whichthe position is being tracked, for example, the type of vehicle, theroad section where the vehicle is located, and so on.

According to an embodiment of the present invention, the encoding schemaupdating device 314 may be configured to compute the probability ofoccurrence of the residues for a specific vehicle according to thenormalized residue distribution-for example, the normal distribution N(μ, σ).

The computation of the probability of occurrence of the residuescorresponding to any specific vehicle in the set S may be conducted intwo phases.

Phase 1, in which the sampling time interval based residue distributionis derived from the normalized residue distribution N (μp, σ).Generally, if the time interval for sampling the position data of acertain vehicle is Δt =t1 −t0, then the sampling time interval At basedresidue distribution is as follows: N′(μ′, σ‘), where μ′=μ*Δt;σ′=σ*(Δt)1/2. For example, if, for a vehicle V1 where thevehicle-mounted terminal 303 is located, the sampling time interval Δtis 15 seconds, then, from the normalized residue distribution N (0.0001,0.00002), it may be derived that the sampling time interval basedresidue distribution corresponding to the vehicle V1 in which thevehicle-mounted terminal 303 is located is normal distributionN′(0.0015, 0.0000775), where the mean value μ′ equals to 0.0015, and thestandard deviation σ′ equals to 0.0000775.

Phase 2, in which the probability of occurrence of the residue iscalculated according to the sampling time interval based residuedistribution. The probability of occurrence of any residue r may becalculated using the cumulative probability function φ corresponding tothe sampling time interval based residue distribution N′(μ′, σ′), asshown in the following formula: φ(r+5*10⁻⁶−μ′)/σ′)−φ(r−5*10⁻⁶−μ′)/σ′) .. . formula (1). For example, to calculate the occurrence frequency ofthe residue Δx=x1−x0, the formula (1) may be used and let r=Δx, therebyobtaining the occurrence frequency of the residue Δx=x1−x0.

As to the cumulative probability function (Cumulative DistributionFunction, CDF) of the standard normal distribution, reference may bemade to “Probability Theory and Mathematical Statistics (J L Devore,2000, Higher Education Press, pp. 149-158). In practical applications,the probability function can be stored in the form of lookup table inthe local memory, such as the storage device 311, in order to realizefast query on the function. In the above it is described how tocalculate the probability of occurrence of residue of position data.

According to an embodiment of the invention, the encoding schemaupdating device 314 may be configured to construct the residue encodingschema according to the probability of occurrence of residue such thateach residue is corresponded to one code and a residue with relativelyhigh probability of occurrence is corresponded to a code of relativelyshort length.

According to an embodiment of the invention, constructing the residueencoding scheme comprises using the Huffman encoding method to encodethe residue. For example, given three residues 15*10⁻⁵, 14*10⁻⁵ and16*10⁻⁵, it is assumed that the probability of their occurrence has beencalculated to be 21%, 18% and 17% respectively. Accordingly, the residueencoding schema may be constructed to make the residues and their codesto have the following corresponding relationships in accordance with thelevel of probability of occurrence: 15*10⁻⁵−“0”; 14*10⁻⁵−“10”;16*10⁻⁵−“110”. Of these three residues, the probability of occurrencefor the residue 15*10⁻⁵ is the highest, and the corresponding code “0”is the shortest. The probability of occurrence for the residue 16*10⁻⁵is the lowest, and the corresponding code “110” is the longest.

Generally speaking, assuming there are n possible residues x1, x2, . . .xn, and the probability of their occurrence is, respectively, f1, f2, .. . , fn. If each of the residues is denoted with a binary number of bbits long, the average length of the n residues is: L =(f1+f2+. . .+fn)*b. According to the residue encoding schema, the correspondingcodes of the residues x1, x2, . . . xn are respectively x1′, x2′, . . ., xn′. Assuming the length of xi′ is li, then the average length of thecodes is: L′=(f1*I1+f2*I2+ . . . +fn*In). In accordance with the laws ofprobability and statistics, L′ is less than L, meaning that the averagelength of all of the codes is less than the average length of theresidues. In other words, using the codes instead of the residues wouldresult in the data compression ratio of L′/L<1.

It should be noted that the present invention may use various frequencydistribution based compression encoding schema. Those skilled in the artshall appreciate that, as long as the encoding schema is made tocorrespond to a source code with high frequency of occurrence to atarget code of short length, the desired effect is achieved. Therefore,the present invention is by no means limited to the Huffman encodingschema.

According to an embodiment of the invention, the decoder 312 isconfigured to generate the corresponding residue of any code inaccordance with the residue encoding schema constructed by the encodingschema updating device 314. In other words, when a code is received fromthe vehicle-mounted terminal, the decoder 312 will generate the residuecorresponding to the code.

The encoding schema updating device 314 is configured to store theconstructed residue encoding schema as the current residue encodingschema in place of the existing residue encoding schema in the storagedevice 311 for use by the decoder 312. Thus, the residue encoding schemaused by the decoder 312 is the updated residue encoding schema. Thefunction of the components of the monitoring server 301 has beendescribed above.

In the following, components of the vehicle-mounted terminal 303 will bedescribed in detail. In general, the vehicle-mounted terminal 303 fortransporting the residue of vehicle position data via a wireless networkaccording to an embodiment of the invention comprises: a dataacquisition device 333 which is configured to obtain the position dataof a vehicle in which the vehicle-mounted terminal is located; anencoding schema updating device 334 which is configured to calculate theprobability of occurrence of the residue corresponding to the vehiclebased on the normalized residue distribution and construct a residueencoding schema according to the probability of occurrence of theresidue such that each residue is corresponded to one code and a residuewith relatively high probability of occurrence is corresponded to a codeof relatively short length; a storage device 331 which is configured tostore the residue encoding schema; and an encoder 332 which isconfigured to generate the corresponding code of any residue accordingto the residue encoding schema stored in the storage device.

The encoding schema updating device 334 of the vehicle-mounted terminal303 has the same function as the encoding schema updating device 314 ofthe monitoring server 301. For example, the encoding schema updatingdevice 334 may calculate the probability of occurrence of the residue ofthe vehicle in which the vehicle-mounted terminal 303 is located basedon μ value and σ value received from the monitoring server 301 thatcharacterize the normal distribution N (μ, σ), and construct a residueencoding schema based on the probability of occurrence of the residuesuch that each residue is corresponded to one code and a residue withrelatively high probability of occurrence is corresponded to a code ofrelatively short length. In other words, the higher the probability ofoccurrence of a residue, the shorter its corresponding code.

The residue encoding schema constructed by the encoding schema updatingdevice 334 will be used by the encoder 332. For example, the encodingschema updating device 334 may store the constructed residue encodingschema as the current residue encoding schema in place of the existingresidue encoding schema in the storage device 311 for use by the encoder332. According to the residue encoding schema used by the encoder 332,residues with higher probability of occurrence correspond to shortercodes, i.e. the higher the probability of occurrence of a residue, theshorter the corresponding code. When the vehicle-mounted terminal 303transmits the code from the encoder 332, the number of times ofrelatively short codes being transmitted is more than the number oftimes of relatively long codes being transmitted, thereby reducing thetotal length of the codes transmitted via the wireless network.

In practical applications, the encoding schema updating device 334 ofthe vehicle-mounted terminal 303 and the encoding schema updating device314 of the monitoring server 301 construct the same residue encodingschema according to the same residue distribution data, the normaldistribution N (μ, σ) for example, as the current residue encodingschema. In this way, synchronization of the residue encoding schema atboth sides of the monitoring server 301 and the vehicle-mounted terminal303 is achieved. The above description has been provided on the functionof various components of the system in accordance with an embodiment ofthe invention, in particular, the function of the data analysis device313 of the monitoring server and the encoding schema updating device 314of the monitoring server and the vehicle-mounted terminal.

Various embodiments of the operation of the system will be furtherillustrated below on the basis of the above description. Referring toFIG. 4, a flowchart of the method according to an embodiment of theinvention is illustrated. The method as shown may be performed by themonitoring server 301 for receiving residues of the vehicle positiondata via a wireless network.

The reference number 400 denotes an initialization step. In this step,the monitoring server 301 performs necessary initialization andestablishes a session with the vehicle-mounted terminal 303 which is tobe tracked. At the beginning, the vehicle-mounted terminal sends aninitial position data to the monitoring server. In response, themonitoring server sends the data for constructing residue encodingschema to the vehicle-mounted terminal for it to generate a residueencoding schema. Meanwhile, the monitoring server also constructs thesame residue encoding schema, thus causing the residue encoding schemaused at both sides of the vehicle-mounted terminal and the monitoringserver to be synchronized.

After the initialization, the monitoring server cyclically performs thefollowing steps. In Step 410, the monitoring server receives, from thevehicle-mounted terminal, the code for residue of position data of thevehicle in which the vehicle-mounted terminal is located. As describedabove, the vehicle-mounted terminal 303 may send the code for residueaccording to the agreement between the vehicle and the monitoring serverand in a predetermined format, so as to compress the amount of data tobe transmitted via the wireless network. For example, the serverreceives, from the vehicle-mounted terminal, binary codes “0” and “10”,which respectively represent the actual value of the residue of x and yin the position data (x, y).

In Step 420, the vehicle position data is derived from the received codeaccording to the current residue encoding schema corresponding to thevehicle in which the vehicle-mounted terminal 303 is located. Forexample, according to the current encoding schema, the code “0”represents the residue 15*10−5 of x in the position data (x, y) and thecode “10” represents the residue 14*10−5 of y in the position data (x,y). According to the residue of the position data (x, y) and thesampling period of the position data as well as historical data, thevehicle's current position data (x1, y1) at a time t1 may be obtained.Obtaining real-time position data (x1, y1, t1) according to residue ofposition data, to which there are already solutions in the prior art, isnot a problem to be solved by the invention and therefore there is noneed to repeatedly describe here. The vehicle position data derived fromthe received code will be stored. In practical applications, thereal-time position data (x1,y1, t1) obtained may be stored in the formof database, together with associated contextual data, into the storagedevice 311 as historical data.

In Step 430, it is determined, according to the environment of thevehicle, whether it is needed to update the current residue encodingschema. Theoretically, the encoding schema may be updated at any time,i.e. a new encoding schema is used in place of the encoding schema beingused at the monitoring server 301 and vehicle-mounted terminal 303. Inpractical applications, a change in the vehicle's environment (e.g.,road section, time, weather) may be taken as the appropriate timing ofupdating the encoding schema. For example, given appropriate division ofroad sections, changes of the driving environment would be little on thesame road section and so would be the vehicle's driving speed. At thistime, it normally does not need to update the encoding schema. If thevehicle enters into another section R2 from a section R1, the drivingenvironment may change greatly and it would be appropriate to update theencoding schema at this time.

According to an embodiment of the invention, said determination ofwhether it is needed to update the current residue encoding schemaaccording to the environment of the vehicle in Step 430 comprises:determining that it is needed to update the residue encoding schema whenit is judged, based on the derived vehicle position data, that the roadsection in which the vehicle is located is changed, for example, fromone road section R1 to another road section R2.

As mentioned in previous paragraphs, with the help of the GIS system,the road section in which the vehicle is currently located can bedetermined according to the mapping relationship between vehicleposition data and road sections in the road network.

If, in Step 430, it is determined that the encoding schema needs to beupdated, the process proceeds to Step 440; otherwise, the processreturns to Step 410. In Step 440, in response to determining that it isneeded to update the current residue encoding schema, the data forupdating encoding schema is generated. According to an embodiment of theinvention, the data for updating encoding schema may be the mean value pand the standard deviation a that characterize a normalized residuedistribution N(μ, σ) of the position data.

As described above with reference to FIG. 3, the data analysis device313 of the monitoring server 301 may generate the normalized residuedistribution of the position data of all vehicles complying with certainconstraints according to historical data. For example, a truck movesinto the road section R2 from the road section R1. As described abovewith reference to FIG. 3, according to the constraint condition {R2,9:00-9:30, truck}, feature values for the normalized residuedistribution satisfying the constraint condition may be generated, forexample, values of the mean value μ=“0.0001” and the standard deviationa “0.00003” for N(0.0001, 0.00003). Of course, if, as described above inconnection with FIG. 3, the following mapping relationship has alreadybeen stored in Hashmap: (R2, {9:00-9:30 truck})-→N (0.0001,0.00003) . .. Mapping (2). Then, the data characterizing the normal distribution N(0.0001, 0.00003), namely the mean value μ=“0.0001” and the standarddeviation σ“0.00003”, may be retrieved directly from the Hashmap.

In Step 450, the data for updating encoding schema, for example, themean value p and the standard deviation a that characterize a normalizedresidue distribution N(μ, φ) of the position data, may be transmitted tothe vehicle-mounted terminal.

In Step 460, the residue encoding schema is constructed based on thedata for updating residue encoding schema, wherein each residue in theresidue encoding schema is corresponded to one code and a residue withrelatively high probability of occurrence is corresponded to a code ofrelatively short length. The current residue encoding schemacorresponding to the vehicle, in which the vehicle-mounted terminal 303is located, is updated with the constructed residue encoding schema.Step 460 may be performed either before or after Step 450.

As previously described with reference to FIG. 3, prior to constructingthe residue encoding schema, the monitoring server 301 has alreadyderived the sampling time interval based residue distribution N′(μ′, σ′)corresponding to the vehicle in which the vehicle-mounted terminal islocated from the normalized residue distribution N (μ, σ).

According to an embodiment of the invention, in Step 350 of transmittingthe data for updating encoding schema to the vehicle-mounted terminal,the mean value μ′ and the standard deviation σ′ that characterize thesampling time interval based residue distribution N′ (μ′, σ′)corresponding to the vehicle in which the vehicle-mounted terminal islocated may be transmitted.

In the above description of the encoding updating device 314 of themonitoring server 301 with reference to FIG. 3, the manner ofconstructing the residue encoding schema based on the data for updatingencoding schema has been described in detail, hence is omitted here. Theconstructed residue encoding schema may be stored in the storage device311 as the current residue encoding schema in place of the existingresidue encoding schema for use by the decoder 312.

The embodiment of the method for transporting the residue of the vehicleposition data via the wireless network performed at the monitoringserver 301 has been described above. Below, with reference to FIG. 5,the method for transporting the residue of the vehicle position data viathe wireless network performed at the vehicle-mounted terminal 303 inaccordance with one embodiment of the invention will be described. Thereference number 500 shows an initialization step. In this step, thevehicle-mounted terminal 303 performs necessary initialization andestablishes a session with the monitoring server 301. As a part of theinitialization, the vehicle-mounted terminal may transmit an initialposition data to the monitoring server. After the initialization, thefollowing steps are performed.

In Step 510, the data for updating encoding schema is received from themonitoring server 301. According to an embodiment of the invention, thedata for updating encoding schema is the mean value μ and the standarddeviation σ that characterize the normalized residue distribution N(μ,σ) of the position data of all vehicles that comply with certainconstraint condition all the position.

In Step 520, a residue encoding schema is constructed based on the datafor updating encoding schema and the constructed encoding schema is usedto take the place of the current encoding schema, wherein each residuein the residue encoding schema is corresponded to a code and a residuewith higher probability of occurrence is corresponded to a shorter code.Step 520 is implemented in substantially the same manner as Step 520performed by the monitoring server 301 as described above with referenceto FIG. 4. According to an embodiment of the invention, said Step 520 ofconstructing a residue encoding schema based on the data for updatingencoding schema comprises: deriving the sampling time interval basedresidue distribution of the vehicle in which vehicle-mounted terminal islocated according to the mean value and the standard deviation; andcalculating the probability of occurrence of residue.

According to another embodiment of the invention, the data for updatingencoding schema is the mean value μ′ and the standard deviation φ′ ofthe sampling time interval based residue distribution N′(μ′,σ′) of thevehicle in which the vehicle-mounted terminal is located. Under thiscircumstance, when constructing a residue encoding schema based on thedata for updating encoding schema, it is possible to calculate theprobability of occurrence of residue directly according to the samplingtime interval based residue distribution. According to an embodiment ofthe invention, said constructing the residue encoding schema comprisesusing the Huffman encoding method for encoding the residue.

In Step 530, the constructed residue encoding schema is stored and madeto be the current residue encoding schema. The constructed residueencoding schema may be stored into the memory device 331 as the currentresidue encoding schemas in place of the existing residue encodingschema for use by the encoder 332. Thereafter, the vehicle-mountedterminal 303 may responds to the need of sending the code for a residueto the monitoring server 310 by selecting the code corresponding to theresidue according to the current residue encoding schema andtransmitting the selected code to the monitoring server 310.

Various embodiments of the method for transporting transmit the residueof vehicle position data residue via the wireless network for executionon the monitoring server 301 and the vehicle mounted terminal 303 aredescribed above. Since the monitoring server 301 and the vehicle mountedterminal 303 have been described in foregoing paragraphs, some of thecontent that is duplicate with the description of the monitoring server301 and the vehicle-mounted terminal 303 is omitted from the descriptionof the method.

Compared with the prior art, the various embodiments of the inventionhave significant technical effect. Using the residue encoding schema inwhich a residue with relative high probability of occurrence correspondsto a relatively short code, the data amount of the code for the residueneeding to be transmitted via the wireless network may be reduced,thereby reducing the bandwidth consumption of the wireless network.

It is to be noted that, according to various embodiments of theinvention, it is not necessary to send the residue encoding schemaitself in order to synchronize the residue encoding schema between themonitoring server and the vehicle-mounted terminal. Rather, what isneeded to be sent may be merely the feature data characterizing theresidue distribution, for example the parameter μ and σa (or μ′and σ′)for the normal distribution, and the wireless network bandwidthconsumption additionally caused is negligible compared with thebandwidth saved.

Embodiments of the invention have been described. The above descriptionis only exemplary, rather than exhaustive or limited to the embodimentsdisclosed. Those skilled in the art shall appreciate that variousmodifications and alterations changes thereto may be readily made. Thechoice of terms herein is intended for best explaining the principle,practical application or improvement to the techniques in the market ofthe embodiments, or allowing those skilled in the art to understandvarious embodiments disclosed herein.

1-15. (canceled)
 16. A vehicle-mounted terminal for transporting residueof vehicle position data via a wireless network, comprising: a dataacquisition device, configured to obtain position data of a vehicle; anencoding schema updating device, configured to calculate a probabilityof occurrence of a residue corresponding to the vehicle according to anormalized residue distribution, and construct a residue encoding schemaaccording to the probability of occurrence utilizing data received froma backend server via the wireless network, thereby producing aconstructed residue encoding schema; a storage device, configured tostore the constructed residue encoding schema; and an encoder,configured to generate a corresponding code of a residue according tothe constructed residue encoding schema; wherein: the vehicle-mountedterminal is located in the vehicle; the constructed residue encodingschema is constructed such that each residue of the constructed residueencoding schema corresponds to one code; and the constructed residueencoding schema is constructed such that a residue with a relativelyhigh probability of occurrence corresponds to a code of relatively shortlength.
 17. The vehicle-mounted terminal of claim 16, whereincalculating the probability of occurrence comprises: deriving a samplingtime interval based residue distribution of the vehicle based on a meanvalue and a standard deviation, which characterize the normalizedresidue distribution; and calculating the probability of occurrenceaccording to the sampling time interval based residue distribution. 18.The vehicle-mounted terminal of claim 17, wherein the mean value and thestandard deviation are received from a monitoring server that ismonitoring the vehicle,
 19. The vehicle-mounted terminal of claim 16,wherein Daidlithe encoding schema updating device is configured to storethe constructed residue encoding schema in the storage device as acurrent residue encoding schema, thereby replacing an existing residueencoding schema.
 20. The vehicle-mounted terminal of claim 16, whereinthe encoding schema updating device is configured to use the Huffmanencoding method to encode a residue.